In general, conventional image forming apparatus such as copiers and laser printers employing an electrophotographic system or electrostatic recording system as described above have a configuration in which image exposure is performed on a surface of a photosensitive drum to form an electrostatic latent image; the electrostatic latent image formed on the surface of the photosensitive drum is developed by a developing device to form a toner image in a predetermined color, and the toner image is directly transferred on to and fixed on recording paper or temporarily transferred to an intermediate transfer body and is thereafter transferred on to the recording paper at a time to form an image.
An example of a conventional image forming apparatus is shown in U.S. Pat. No. 6,349,192 to Yoshino et al. In such apparatus, when a color image is formed by an image forming apparatus 500, as shown in FIG. 5 herein, a configuration may be employed in which a latent image forming step of performing image exposure on a surface of a single photosensitive drum 300 with an image exposure device 301 to form an electrostatic latent image associated with a predetermined color and a developing step of developing the latent image with a developing device for the associated color are repeated for a predetermined number of colors; toner images having the predetermined colors sequentially formed on the surface of the photosensitive drum are subjected to primary transfer onto an intermediate transfer belt on a multiplex basis; and the toner images are subjected to secondary transfer from the intermediate transfer belt on to a substrate media at a time to form a color image.
Image forming apparatus include so-called tandem type image forming apparatus having plural (e.g., four) photosensitive drums each associated with a predetermined color and having a configuration in which toner images in predetermined colors sequentially formed on surfaces of the respective photosensitive drums are subjected to primary transfer on to an intermediate transfer belt 2 on a multiplex basis; and the toner images are thereafter subjected to secondary transfer from the intermediate transfer belt on to a substrate media 7 at a time to form a color image. For example, FIG. 5 shows a tandem type image forming apparatus having four image forming units 300, i.e., individual forming units for colors such as black (K), yellow (Y), magenta (M) and cyan (C). The four image forming units 300 are horizontally arranged at constant intervals from each other. Below the image forming units for the colors, an intermediate transfer belt 2 for transferring toner images sequentially formed by the respective image forming units in an overlapping relationship with each other is provided such that it is driven by plural rolls 200-203 including driving rolls for rotation in the direction indicated by the arrow. For example, the intermediate transfer belt 2 is configured in the form of an endless belt by forming a synthetic resin film made of polyimide or the like having flexibility in the form of a belt and by connecting both ends of the synthetic resin film formed in a belt-like configuration by means of welding or the like.
In printing systems, transfer belts are also used to handle and/or transfer substrate media as well as the images for transfer to the substrate media. Thus, an image can be transferred after being deposited on a substrate media. As with the intermediate transfer belts described above, such substrate media transfer belts 3 move along a travel path in a process direction and are supported by various rollers or support shoes intended to maintain the belts in position. However, sometimes due to heavy usage, poor belt conicity or hardware misalignments the belts can slide or shift laterally on the rollers that drive them. Such lateral movement can lead to belt walk-off, where the belt comes off the rollers, which can in-turn lead to operating delays as well as possible damage to the belt, substrate media or the system itself.
In certain printing systems that use transfer belts, edge guides are used to limit lateral movement. However due to extensive usage and the fragile nature of the belts, edge guides can compromise the integrity of the belt as well. Alternatively, belt edge detectors are employed to track lateral belt movement and potentially shut-down the system before the belt walks off a roller. While belt edge detectors are helpful in preventing damage to the belt or the system, they do not automatically correct the improper belt position. Also, the manual adjustment or re-adjustment of a belt or the belt roller pitch can be time consuming and negatively effect production deadlines.
Accordingly, it would be desirable to provide an apparatus or method of controlling and/or adjusting the lateral position of one or more belts in a printing system in order to avoid processing interruptions or delays, damage to the system or substrate media and other shortcomings of the prior art.